1. Field of the Invention
The present invention relates to a method of, and an apparatus for, mounting a vehicular window glass (or window pane) on a window portion in a vehicle body of a vehicle such as a motor vehicle or the like by means of an adhesive agent, particularly by means of a hot melt type of adhesive agent (hereinafter called a hot melt adhesive agent).
2. Description of the Related Art
As can be seen in Japanese Published Unexamined Patent Application No. 81641/1995, there has hitherto been known a method of mounting a window glass, which has applied or coated thereto an adhesive agent, on a window portion by pushing or forcing the window glass to a window frame of the window portion in a state in which the window glass is held by a jig which is mounted on a robot.
As the adhesive agent for the window glass, there is ordinarily used a moisture-hardened adhesive agent. However, since it takes time to harden the adhesive agent, the window glass is conventionally temporarily held in position by attaching a temporary holding member such as a fastener, or the like. This method has a disadvantage in that the number of parts and the number of working steps increase.
If a rapid-hardening adhesive agent is used, the temporary holding member becomes unnecessary, whereby the above-described disadvantage can be eliminated. The rapid hardening adhesive agent is also used in the art described in the above-described Published Unexamined Japanese Patent Application No. 81641/1995. However, since this adhesive agent has a high initial viscosity, fluctuations occur in the thickness of a bead of the adhesive agent when the bead is crushed (i.e., pushed or forced out of shape) by the pushing of the window glass. Therefore, the control of the pushing force becomes troublesome.
As a solution, there has recently been used a hot melt type of one-liquid urethane adhesive agent which has added thereto a thermoplastic resin. Since this adhesive agent is low in initial viscosity, the control of the pushing force becomes easy. In addition, the viscosity of the adhesive agent increases with a lowering (or decrease) in the temperature of the adhesive agent. Therefore, there can be obtained a function of temporarily holding the window glass, and there is an advantage in that the temporary holding member becomes unnecessary.
While the hot melt adhesive agent has various advantages as described hereinabove, it has also the following disadvantages. Namely, the temperature of the adhesive agent lowers between the time of applying the adhesive agent to the window glass and the time of pushing the window glass to the window frame, resulting in too high a viscosity. If the temperature of the adhesive agent is increased, it takes time before the temporary holding function can be obtained, resulting in a troublesome temperature control.
Furthermore, if the hot melt adhesive agent that has been applied to the window glass comes into contact with the window frame, the hardening of the adhesive agent is accelerated by the temperature decrease due to thermal shrinkage. As a result, the pushing force required to crush the bead of the adhesive agent to a required thickness increases. Here, in case there is provided a jig for the window glass at a front end of a robot arm, there is applied to the front end of the robot arm a pushing reaction force in a direction which is normal to the window portion. With the increase in the pushing force, the bending moment which is applied to the robot arm also increases. Then, due to the deflection of the robot arm by the bending moment, the jig is tilted in the direction in which the bending moment is applied, with the result that the window glass can no longer be mounted in an ordinary pushed state.
In view of the above-described points, the present invention has an object of facilitating a satisfactory mounting of a window glass only by controlling the temperature of an adhesive agent when the adhesive agent is applied to the window glass, and also to facilitate the mounting of the window glass to the window portion of the vehicle body in a normal pushed state even if a deflection occurs to a robot arm.